Circuit breaker trip and latch mechanism

ABSTRACT

A circuit breaker with a thermal and magnetic tripping mechanism for releasing the separable contacts of the circuit breaker in response to overload currents. The tripping mechanism comprising a trip bar responsive indirectly to the overload current for releasing a trip lever which in turn releases a latch lever. The latch lever and trip lever being pivoted on spaced pivot points and the trip lever having a roller mounted thereon for retaining the latch lever in the latched position and for rolling out of engagement with the latch lever when the trip lever is released, whereby shorter levers and less force are required to actuate the mechanism.

United States Patent [1 1 Walker et a].

[ CIRCUIT BREAKER TRIP AND LATCH MECHANISM Inventors: Eugene J. Walker,Beaver; Alfred E.

Maier, Beaver Falls, both of Pa.

Westinghouse Electric Corporation, Pittsburgh, Pa.

Filed: Mar. 27, 1973 Appl. No: 345,396

Assignee:

US. Cl. 335/167, 335/191 Int. Cl. H0lh 9/20 Field of Search 335/167,168, 169, 170,

References Cited UNITED STATES PATENTS Frank... 335/191 Yorgin et al335/173 8/1936 Coleetal......' 335/168 [4 1 May 7,1974

3,657,672 4/1972 Flick et al 335/168 Primary Examiner-Harold BroomeAttorney, Agent, or FirmL. P. Johns [57] ABSTRACT A circuit breaker witha thermal and magnetic tripping mechanism for releasing the separablecontacts 7 Claims, 7 Drawing Figures III CIRCUIT BREAKER TRIP AND LATCHMECHANISM CROSS REFERENCE TO RELATED APPLICATIONS This invention isrelated to the invention disclosed in the application of Alfred Maier etal., Ser. No. 345,394, filed Mar. 27, 1973.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to a circuit breaker having a trip and latch mechanismresponsive to thermal and magnetic forces.

2. Description of the Prior Art Circuit breakers of the type disclosedin US. Pat. No. 3,530,414 comprise overcurrent protective devices thatfunction satisfactorily for responding to such abnormal currents asovercurrents, ground fault currents, and short currents that occur in anelectrical distribution system. Certain disadvantages have developed,however, with that type of construction including augmented size foroperating parts with the development of additional overcurrentprotective means.

SUMMARY OF THE INVENTION Generally, it has been found in accordance withthis invention that the foregoing disadvantage may be overcome byproviding a protective device for a circuit breaker which comrpisesrelatively movable contact means and means releasable to effect openingof said contact means, the releasable means including a releasable armmovable between latched and unlatched positions, a trip device operableto effect unlatching of the releasable arm, the trip devicecomprisingmagnetic trip means, a trip bar, a latch lever, and a triplever, the atch lever being movable between latched and unlatchedpositions of the releasable arm and being biased in the latched positionand being urged to the unlatched position by the releasable arm, thetrip lever being movable between latched and unlatched positions of thelatch lever and being in the latched position, the latch lever beingretained in the latched position by the trip bar, a pin rotatablymounted on the trip lever and located in the path of movement of thelatch lever to retain the latch lever in the latched position when thetrip bar is in the latched position, and the pin being in rotatablecontact with the latch lever as the latch lever moves to the unlatchedposition when the trip lever is unlatched'by the trip bar, whereby therotatable pin minimizes the frictional forces between the trip lever andthe latch lever upon movement of the latch lever from the latched to theunlatched position.

The advantage of the device of this invention is that it reduces thelatch load on the trip bar and enables the use of shorter levers andless force, which in turn provides for a more compact operative device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is -a vertical sectional viewof a circuit breaker;

FIG. 2 is a right elevational view of the trip device;

FIG. 3 is a left elevational view of the trip device;

FIG. 4 is a vertical sectional view taken on the line IVIV of FIG. 3;

FIG. 5 is a vertical sectional view taken on the line V-V of FIG. 3;

FIG. 6 is a plan view of the trip device shown in FIGS. 2-5; and

FIG. 7 is a vertical sectional view taken on the line VII-VII of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a circuit breaker isgenerally indicated at 3 and it comprises an insulating housing 5 and acircuit breaker mechanism 7 supported within the housing. The housing 5comprises an insulating base 9 and an insulating cover 11.

The circuit breaker mechanism 7 comprises an operating mechanism, and alatch and trip device 15. Except for the latch and trip device, thecircuit breaker 3 is of the type that is generally described in thepatent to Albert R. Cellerini et al., U.S. Pat. No. 3,287,534 issuedNov. 22, 1966. The circuit breaker 3 is a threepole circuit breakercomprising three compartments disposed in side-by-side relationship, thecenter pole compartment (FIG. 1) is separated from the two outer polecompartments by insulating barrier walls formed with the housing base 9and cover 11. The operating mechanism 13 is disposed in the center polecompartment and is a single operating mechanism for operating .thecontacts of all three pole units.

Each pole unit comprises a stationary contact 21 that is fixedly securedto a rigid main conductor 23 that in turn is secured to the base 9 bybolt 25. In each pole unit, a movable contact 27 is welded or brazed toa contact arm that is mounted on a switch arm 31 by a pivot pin 33. Thearms 29 and 31 for all three of the pole units are supported at one endthereof and rigidly connected on a common insulating tie bar 35 by whichthe arms of all three pole units move in unison. Each of the contactarms 29 is biased about the associated pivot pin 33 by means of a spring37 to provide contact pressure in the closed position.

The operating mechanism 13 actuates the switch arms 31 between open andclosed positions.'The mechanism comprises a pivoted formed operatinglever 39, a toggle comprising two toggle links 41 and 43, overcentersprings 45 and 47, and a pivoted releasable cradle or arm 49 controlledby the trip device 15. An insulating shield 51 forsubstantially closingan opening 53 in the cover 11, is mounted on the outer end of theoperating lever 39 and has an integral handle portion 55 extending outthrough the opening to enable manual operation of the breaker. Thetoggle links 41 and 43 are pivotally connected together by a knee pivotpin 57. The toggle link 41 is pivotally connected to the releasable arm49 by a pin 59, and the toggle link 43 is pivotally connected to theswitch arm 31 of the center pole unit by a pin 61. The overcentersprings 45 and 47 are connected under tension between the knee pivot pin57 and the outer end of the operating lever 39. The circuit breaker ismanually operated to the open position by movement of the handle portion55 in a counterclockwise direction to the off" position, which movementactuates the overcenter springs 45, 47 to collapse the toggle links 41and 43 to the position shown in FIG. 1, and opening movement of thecontact arm 29 for all of the pole units in a manner well known in theart.

The circuit breaker is manually closed by reverse movement of the handleportion 55 from the off" position to the on position, which movementcauses the springs 45, 47 to move over center and straighten the togglelinks 41, 43 thereby moving the contact arm 29, for all of the poleunits, to the closed position as shown in broken line position.

The trip device serves to effect automatic release of the releasablecradle or arm 49 and opening of the breaker contacts for all of the poleunits, in response to predetermined overload conditions in the circuitbreaker through any or all pole units of the circuit breaker, in amanner described hereinbelow.

The circuit through each pole unit extends from a right-hand terminal 63through the conductor 23, the contacts 21, 27, the contact arm 29, aflexible conductor 65, that is secured to the contact arm 29, aconductor 67, a trip conductor 69, to a left-hand terminal connector 71.Bolt means 73secure one end of the trip conductor 69 to the conductor 67and the other end of the trip conductor 69 is disposed between a backupplate 75 and the terminal 71 where it is secured in place by mountingbolt 77 of the terminal 71.

As shown in FIGS. 2-6 the latch and trip device 15 comprises a moldedinsulating housing base 81 and a molded insulating housing cover 79secured to the base to enclose a molded insulating trip bar 83 that iscommon to all three of the pole units. As shown in FIG. 3, the base 81includes a pair of spaced partitions 85 and 87 which are verticallydisposed and integral with the base for separating the interior of thehousing into three compartments, each compartment containing one of thethree poles. In a similar manner, the cover 79 is provided withpartitions corresponding to partitions 85 and 87 and have matingsurfaces therewith in a manner similar to the mating surfaces of theperipheral surfaces of the base 81 and cover 79 as indicated by aparting line 89 (FIG. 6). i

As shown in FIG. 3, the partitions 85 and 87 have notches 91 and 93,respectively, which together'with flat surfaces of the cover 79 serve asjournals for round shaft portions 95 and 97 of the trip bar 83.Accordingly,'when the'housing base 79 and cover 79 are assembled theyretain the trip bar 83 in place, whereby the trip bar is free to rotateon an axis extending through'the shaft portions 95 and 97. As shown moreparticularly, in FIG. 5, each section of the trip bar 83 located withinthe space compartments of the housing comprise upper and lower portions83a and 83b, which are above and below the axis of rotation of the tripbar. Each upper portion 83a is provided with an adjusting screw and nutassembly 99 which cooperates with a bimetal member 101 for adjusting thespacing between the upper ends of the bimetal member and the trip barportion 83a in response to the degree of deflection of the upper end ofthe member 101 toward the member 7 83a, whereby the trip bar-83 isrotated clockwise by the bimetal member and thereby trips the circuitbreaker to the open position. The lower end portion 83b of the trip bar83 is preferably provided with a drive screw 103 by which contact ismade with an adjoining mem-' bet for similar rotation of the trip bar inthe manner to be described hereinbelow.

As shown more particularly in FIG. 5, the trip conductor 69 includes aninverted U-shaped intermediate portion 69a which constitutes a singleloop of a stationary magnetic structure. Stationary magnetic structurealso comprises a magnetic core 105, a U-shaped frame 107 having a pairof spaced flanges 109 one of which is shown in FIG. 5, and an armature111. The assembly of the intermediate U-shaped portion 69a, the core105, and the intermediate portion of the frame 107 together with thelower portion of the bimetal member 101 are secured in place by suitablemeans such as rivets 113 on the housing base 79. The lower end portionof the bimetal member 101 is in surface to surface contact with theconductor 69, whereby upon the occurrence of a low persistent overloadcurrent below a predetermined value, of, for example, 10 times normalrated current, the bimetal member 101 is heated and deflects to theright through an air gap dependent upon the setting of the adjustmentscrew 99. Thus,'when' a' low persistent overload current occurs, thetrip bar 83 is actuated to trip the circuit breaker.

The armature 111 is disposed between the space flanges 109 of theU-shaped frame 107 and is pivotally mounted therein to rotate about anaxis 115 near the lower end of the armature. For that purpose, thearmature 111 is preferably mounted by suitable means such as rivets 117on 'a support lever 119 having oppositely extending out-turned lugs 121which are seated in corresponding openings 123 in the flanges 109. Eachflange 109 is also provided with a V-shaped notch 125 into which edgeportions of the lever 119 and armature 11] extend. The notches 125thereby limit movement of the assembly of the lever 119 and armature 111when the armature is attracted toward the core 105. Accordingly, theassembly of the lever 119 and armature 111' which is biased in theclockwise direction by coil springs 127 (FIG. 3) is movablecounterclockwise against the spring to engage the drive screw 103 andthereby rotates the trip bar 83 clockwise. When an overload currentabove a value such, for example, as ten times normal rated current or ashort circuit current occurs, the stationary magnetic structure isenergized and the armature 111 is attracted toward the core 105 causinginstantaneous release of the releasable arm 49 and opening of thecontacts 21 and 27.

In addition to the foregoing, means are provided for I adjusting thespacing between the armature 111 and the core 105, whereby upon maximumspacing of the armature from the core, a greater current overload isrequired to attract the armature toward the core. Conversely, when thespacing is reduced, a smaller overload current is required to actuatethe trip bar 83. For that purpose a lever 129 having a lower enddisposed over the upper end of the lever 119 is mounted within thehousing and is provided with calibration means including a calibrationscrew 131 at the upper end of the lever 129. As shown in FIG. 3, eachlever 129 includes a notch 133 on each opposite side thereof which notchis seated in corresponding projections 135 of the housing base 79 wherethe levers 129 are retained in place by the cover 81. An adjusting knob137 is seated within the top end of the housing base and is providedwith a lower end portion having a cam surface. Inasmuch as the lever 129is biased counterclockwise about its pivot point by the spring 127 ofthe lower lever 119 the calibration 131 rides on the cam surface of thelower portion 139 of the adjusting knob 137.

As shown in FIG. 3 and 5, each adjusting knob 137 includes a flange 141,the lower surface of which includes spaced notches 143. An index member145 is disposed below the flange 143 and is provided with a projection147 for engaging one of the spaced notches 143 as the calibrating screw136 is rotated to the desired position. Accordingly, the desired spacingbetween the armature 111 and the core 105 is established by rotation ofthe adjusting knob 137.

Since the housing cover 79 is used to hold the levers 129 in place, itis necessary to assemble the trip unit completely before calibrating theposition of the lever 129. For that reason, a removable flexible shield149 is disposed in an access opening 151 of the cover 79 in order toturn the calibrating screw 131 and 99. When the calibration is made, theshield 149 is replaced in the opening. The mechanism by which thereleasable arm 49 is released is shown in FIG. 2, 4 and 6. The mechanismincludes the trip bar 83, a trip lever 153 and a latch lever 155. AU-shaped mounting frame 157 is mounted on the base 79 with spacedupright sides 157a and 157b providing mounting support for the levers.The trip lever 153 includes a U-shaped portion 159 at the lower endwhich portion is mounted on a pivot pin 161 which extends from the side157a of the frame. The U-shaped lower portion of the lever maintains thelever upright adjacent the frame side 1570. The upper end of the triplever 153 includes a flange 163 which engages a notch 165 on the tripbar 83. As shown in FIG. 4 a portion of the trip bar extends through anopening 167 in the insulating base 79.

The latch lever 155 includes down-turned portions 155a and 15512 whichare mounted on a pivot pin 169 the opposite ends of which are secured inthe sides 157a and 157b of the frame 157. A spring 171 is mounted on thepin 169 and has end portions engaging the levers 153 and 155 for biasingthe levers in the latched positions.

When the releasable arm 49 is in the latched position as shown in FIG.1, the arm which is pivoted on a pivot pin 173 is secured in the latchedposition below the lever 155 and applies a rotatable force thereon.

As shown in FIGS. 4 and 7, the latch lever 155 is prevented from turningdue to engagement of the lower end of the lever on a roller or rotatingpin 175 which is mounted in the U-shaped portion 159 of th trip lever153. As a result of the rotating force on the latch lever 155, the triplever 153 is biased clockwise and is prevented from movement by engagingof the flange 163 in the notch 165 of the trip bar 83. When the trip baris rotated clockwise, the flange 163 is dislodged from the latchposition within the notch 165 and the trip lever 153 rotates clockwiseto move the roller 175 from engagement with the lower end of the latchlever 155. As a result, the latch lever 155 is free to rotate about thepin 169 and thereby unlatch the releasable arm 49 from th latchedposition.

As the roller 175 moves from engagement with latch lever 155, the rollerrotates and thereby minimizes friction between these parts. Thus, thelength of the levers can be shortened as compared with levers used witha nonrotating pin; and a more compact structure is obtained.

In FIG. 3, a projection 177 extends from the upper corner of the tripbar portion 83a, which projection is aligned with an aperture 179 in thehousing base 79. By

6 extending a pin through the opening 179 (FIG. 2), and pressing againstthe projection 177, the trip bar may be tripped manually.

Accordingly, the device of the present invention provides a new andnovel trip device for a circuit breaker which is of a more compact sizethan the previous trip devices of the same rating. The advantage of thesmaller dimensions is due primarily to the use of lever means havingsmaller space requirements than magnetic tripping devices of priorconstruction. As a result of the more compact arrangement of parts, theouter dimensions of the circuit breaker housing may also be reduced forcircuit breakers of the same rating.

What is claimed is:

l. A circuit breaker comprising relatively movable contact means andmeans releasable to effect automatic opening of said contact means, thereleasable means including a releasable arm movable between latched andunlatched .positions, a trip device operable to effect unlatching of thereleasable arm, the trip device comprising magnetic trip means, a tripbar, a latch lever, and a trip lever, the latch lever being movablebetween latched and unlatched positions of the releasable arm an beingbiased in the latched position and being urged to the unlatched positionby the releasable arm, the trip lever being movable between latched andunlatched positions of the latch lever and being biased in the latchedposition, the trip lever being retained in the latched position by thetrip bar, a pin rotatably mounted on the trip lever and located in thepath of movement of the latch lever to retain the latch lever in thelatched position when the trip bar is in the latched position, and thepin being in rotatable contact with the latch lever as the latch levermoves to the unlatched position when the trip lever is unlatched by thetrip bar, whereby the rotatable pin minimizes the frictional forcesbetween the trip lever and latch lever upon movement of the latch leverfrom the latched to the unlatched positions.

2. The circuit breaker of claim 1 in which the distance between thepivot point and the trip bar contact of the trip lever is greater thanthe distance between the pivot point and the releasable arm contact ofthe latch lever.

3. The circuit breaker of claim 2 in which the rotatable pin is nearerthe pivot point of the trip leverthan is the trip bar.

4. The circuit breaker of claim 3 in which the distance between thepivot point of the latch lever to the rotatable pin is greater than thedistance between said pivot point and the contact of the latch lever andthe releasable arm.

5. The circuit breaker of claim 1 in which the latch lever comprises aflange that is substantially parallel to v trip bar to the unlatchedposition.

1. A circuit breaker comprising relatively movable contact means andmeans releasable to effect automatic opening of said contact means, thereleasable means including a releasable arm movable between latched andunlatched positions, a trip device operable to effect unlatching of thereleasable arm, the trip device comprising magnetic trip means, a tripbar, a latch lever, and a trip lever, the latch lever being movablebetween latched and unlatched positions of the releasable arm an beingbiased in the latched position and being urged to the unlatched positionby the releasable arm, the trip lever being movable between latched andunlatched positions of the latch lever and being biased in the latchedposition, the trip lever being retained in the latched position by thetrip bar, a pin rotatably mounted on the trip lever and located in thepath of movement of the latch lever to retain the latch lever in thelatched position when the trip bar is in the latched position, and thepin being in rotatable contact with the latch lever as the latch levermoves to the unlatched position when the trip lever is unlatched by thetrip bar, whereby the rotatable pin minimizes the frictional forcesbetween the trip lever and latch lever upon movement of the latch leverfrom the latched to the unlatched positions.
 2. The circuit breaker ofclaim 1 in which the distance between the pivot point and the trip barcontact of the trip lever is greater than the distance between the pivotpoint and the releasable arm coNtact of the latch lever.
 3. The circuitbreaker of claim 2 in which the rotatable pin is nearer the pivot pointof the trip lever than is the trip bar.
 4. The circuit breaker of claim3 in which the distance between the pivot point of the latch lever tothe rotatable pin is greater than the distance between said pivot pointand the contact of the latch lever and the releasable arm.
 5. Thecircuit breaker of claim 1 in which the latch lever comprises a flangethat is substantially parallel to the axis of rotation of the latchlever, and the releasable arm being held in the latched position by theflange.
 6. The circuit breaker of claim 1 in which the latch lever andtrip lever are rotatable on parallel axis.
 7. The circuit breaker ofclaim 1 in which the trip device comprises a bimetal strip having oneend mounted on the conductor and another end disposed in a positionadjacent to the trip bar to effect movement of the trip bar to theunlatched position.